Guides / Process

Grinding Tungsten and Tungsten Carbide Versus CNC Milling and Turning

September 21, 2026 · Reviewed September 26, 2026

Milling and turning cover most of the tungsten and tungsten heavy alloy parts this site sources, but grinding is the right process for a specific subset of jobs: sintered tungsten carbide almost always, and the tightest tolerance or most brittle features on pure tungsten and heavy alloy sometimes. Knowing which category your part falls into before you send a drawing saves a round trip with the shop.

Why sintered tungsten carbide cannot be milled

Tungsten carbide (WC-Co) is a sintered composite of tungsten carbide particles in a cobalt binder, and after sintering it reaches a hardness that standard milling and turning tools cannot cut. This is the same hardness that makes carbide useful as a cutting tool material in the first place; a milling cutter cannot remove metal from a workpiece harder than itself. Two approaches work around this:

• Machine before sintering. A carbide part can be pressed and lightly shaped while still a soft powder compact, before the sintering step that hardens it. This works well for simple geometry established early in the process but cannot correct features after the part has been sintered.
• Grind or EDM after sintering. Diamond grinding wheels, which are harder than sintered carbide, remove material by abrasion rather than cutting. Wire and sinker EDM erode material electrically and do not depend on the tool being harder than the workpiece, which makes EDM useful for shapes grinding cannot reach, such as small internal features.

A drawing calling for milled slots, pockets or drilled holes on finished sintered carbide is describing an operation most shops cannot perform as specified. If your design needs those features on carbide, expect the quote to come back proposing grinding, EDM, or a design change to machine the feature before sintering instead.

When pure tungsten and heavy alloy need grinding too

Unlike carbide, pure tungsten and tungsten heavy alloy are milled and turned successfully every day, using carbide tooling on standard CNC equipment. Heavy alloy machines much like hard cast iron, and pure tungsten machines with more care due to its brittleness but still primarily by milling and turning. Grinding becomes the better process for these materials in narrower circumstances:

• Tolerances tighter than milling reliably holds. Standard milled tolerance on pure tungsten runs around ±0.025 mm and on heavy alloy around ±0.01 to ±0.025 mm. A feature specified tighter than that, particularly on pure tungsten, is more reliably held by a finish grinding pass than by pushing a milling operation past its practical limit.
• Fine surface finish requirements. Some optical, sealing or precision fit applications need a finish smoother than a milled surface reliably delivers, which points to grinding as a finishing step after the part is roughed to near-final size by milling.
• Thin, brittle sections on pure tungsten. A thin wall or fine feature prone to chipping under milling forces sometimes finishes better under the lighter, more controlled material removal of grinding, particularly on the last few thousandths before final size.

In practice, most heavy alloy parts and a large share of pure tungsten parts never need grinding at all. It is a finishing step reserved for the tightest features on a drawing, not a replacement for milling across the whole part.

Material	Primary process	When grinding is added
Tungsten heavy alloy	Milling and turning	Rarely, only for the tightest tolerance features
Pure tungsten	Milling and turning	Sometimes, for tight tolerance or fine finish on brittle sections
Tungsten carbide (sintered)	Grinding and EDM	Standard process after sintering; milling is not viable

Reading a drawing for grinding needs

A shop quoting your part looks at a few signals to decide whether grinding is needed:

1. Material. Sintered carbide defaults to grinding and EDM as discussed above.
2. Tightest tolerance on the drawing, not the average. A single tight-tolerance diameter or bore on an otherwise ordinary heavy alloy part can be the one feature that needs a grinding pass while the rest of the part is milled.
3. Surface finish callout, expressed as a roughness value if your drawing specifies one. A finish tighter than a standard milled surface achieves points toward grinding regardless of the dimensional tolerance.
4. Feature geometry. Internal features, small radii and deep narrow slots that grinding wheels cannot reach may need EDM instead of grinding even when the tolerance would otherwise call for it.

If you are not certain which of your features need grinding, the more useful step is to make sure the tolerance and finish callouts on the drawing are complete and unambiguous, and let the shop identify which operations the part actually needs during quoting. Guessing at the process yourself before the shop sees the full drawing can lead to over-specifying grinding on features that would mill just fine.

Sourcing a part with grinding requirements

State the material, the tightest tolerance, and any explicit finish requirement clearly on your RFQ. If your part is sintered carbide, say so directly, since this changes which shops can quote it at all. For heavy alloy or pure tungsten parts with one or two tight features among otherwise standard tolerances, note those features specifically so the shop can price the grinding operation separately from the milling work.

When your drawing is ready, send your RFQ and we match it with shops set up for grinding and EDM alongside milling and turning. For where wire EDM specifically fits into machining tungsten parts, see wire EDM for tungsten parts. For general tolerance guidance across grades, see tungsten machining tolerances and finish.

Frequently asked questions

Sources

• Wikipedia - Grinding (abrasive cutting)
• Wikipedia - Tungsten carbide

Keep reading

• Thin Tungsten Plate and Foil: How Shops Machine It Without Cracks or Warp
• Grinding Tungsten Heavy Alloy: Which Wheel, What Finish, How Tight